Kathleen Sebelius - who weathered heavy criticism over the flaw-filled launch of the Obamacare website, then saw the program through as it topped a major milestone - is resigning as secretary of the Department of Health and Human Services, a White House official said Thursday.

President Barack Obama intends to nominate Sylvia Mathews Burwell, current director of the Office of Management and Budget, to replace Sebelius, according to the official.

A former Kansas governor and, before that, state insurance commissioner, Sebelius was sworn in as HHS secretary in April 2009.

Her time as head of the federal health agency coincided with the passage and implementation of the Affordable Care Act, the bill often referred to as Obamacare.

Sebelius came under fire last fall for the rocky rollout ofHealthCare.gov, the website central to the new law's implementation.

Stop worrying about the website and start talking about Obamacare's benefits.

That was President Barack Obama's message to the nation on Tuesday as he kicked off a three-week public relations blitz intended to generate more participation in his signature health care reforms, reports CNN's Brianna Keilar.

A day after officials declared the previously dysfunctional HealthCare.gov website working smoothly for most users, Obama held a White House event to try to shift the focus of a fiercely partisan public debate to how much help the 2010 Affordable Care Act offers Americans in need.

He noted the botched website launch of October 1 set back implementation of the reforms, and encouraged supporters to help him reintroduce the law to a still skeptical nation.

"Our poor execution in the first couple months on the website clouded the fact that there are a whole bunch of people who stand to benefit," Obama said. "Now that the website's working for the vast majority of people, we need to make sure that folks refocus on what's at stake here."

The administration hopes the new ability of HealthCare.gov to handle 800,000 users a day or more without major problems signals a major step forward in getting people to sign up for health coverage now required by law under the reforms.

"The White House seems to think it's going well so far, but they also acknowledge the real proof is going to be in the December enrollment numbers, Keilar reports. "That's really their focus now that they're turning the page from the troubled website."

However, officials including Obama, warn that glitches will persist and describe the website as a work in progress.

The White House is faced with two more embarrassing revelations in the never-ending Obamacare fiasco.

First, newly released documents reveal a private consulting firm warned the administration that the Healthcare.gov website could be a disaster - way back in spring.

And second, in a CNN exclusive, a Washington state mom–hailed as an Obamacare “success story” by the president in a speech just last month–says now she can't afford the insurance and blames the state exchanges, CNN's Jim Acosta reports.

Obama is expected by former administration officials to soon make a course correction in his administration to address the glaring mistakes made in the roll-out of the Affordable Care Act.

"I think they're going to have to hold somebody accountable for the botched roll-out and the website not working –somebody at HHS or a group of people," said Robert Gibbs, Obama's press secretary during his first term, on NBC's "Today" show on Monday.

"I think if this were to happen in the private sector, somebody would have probably already lost their job and I think the only way to restore ultimate confidence in going forward is to make sure that whoever was in charge of this isn't in charge of the long-term health care plan," Gibbs said.

The White House tried to woo young Americans into the new health exchanges Monday night, releasing a study suggesting nearly half of eligible Americans between 18 and 34 can purchase coverage for less than $50 per month.

The administration is also extending the signup window by six weeks, reports CNN’s Brianna Keilar. She says, “That signup deadline is now March 31st”, it had been February 15th.”

The study also helps to push back against consumer tales of Obamacare sticker shock and frustration of some Americans that their current health plans can't continue under the new law.

But one insurance industry source told CNN the vast majority of Americans on the individual insurance market will see modifications to their existing plans, or even cancellations.

For months, Obama administration officials have asserted that in order for the new exchanges to be a success, roughly 40 percent of the customers needed to be young and healthy.